The invention relates to a method, an apparatus, and a solution for the selective removal of metal or other materials from surfaces of a substrate after the substrate has been subjected to a metal or other material deposition operation. More particularly, the present invention relates to a method, apparatus and solution to remove metal from surfaces where the presence of such metal is undesirable. In doing so, the present invention helps to prevent contamination of elements of a processing line as the undesired material separates from the surfaces.
In the production of microelectronic devices, packages, flat panels, among other articles, one or more metals, alloys, and/or materials may be deposited on surfaces for a variety of purposes. Typically, it is desirable for metal to be deposited only in certain locations and not in others. Metal deposited outside of desired locations may lead to defects in semiconductor devices. Also, metal or other materials absorbed, adsorbed, and/or deposited outside of desired locations may result in contamination of elements of a semiconductor device fabrication facility.
Furthermore, metal deposited on areas where it is not meant to be deposited may not adhere properly. For example, copper has poor adhesion to most insulators. As a result, the poorly adhered metal may easily be separated from the semiconductor substrate or package causing contamination to the semiconductor device fabrication line. Also, copper ions may adsorb on dielectric surfaces, and may be sheared or transferred to other surfaces during subsequent operations.
As a result of metal, such as copper, gold, silver, nickel, palladium and/or platinum deposited outside of desired areas, metal, for example copper, and/or other material, such as resin and/or resist residues, that is deposited, absorbed, and/or adsorbed on edges and/or backsides or other surfaces of a semiconductor wafer or other substrate where it is not desired that the metal be deposited may flake off of or otherwise be separated from the substrate. The flaked off materials and/or metal may act as a source of particulate that may then contaminate deposition equipment and/or other subsequent apparatus and equipment that is exposed to the semiconductor wafer or other substrate. Particulates or undesirable metal or other material contamination of devices may result in degraded chip and package yield, degraded performance, and expensive equipment or factory clean up operations. Also, expensive operating protocols may be necessary to minimize or reduce particulate and unwanted materials contamination problems.
An additional problem related to unwanted metal deposition is tool cross-contamination and line contamination. These problems may be caused by improperly deposited metal on a substrate randomly falling off to surfaces to where they are least desired to be. For example, metal and/or other material may flake off on surfaces on a robot handler. It may also be transferred by the shearing action, as the backside of a wafer to equipment and/or robot end effector.
Copper, like gold and other metals that form deep trapping centers in semiconductor devices are not generally welcomed in semiconductor lines. However, as the use of copper for chip interconnect wiring applications gains more acceptance, the potential for copper contamination and cross-contamination of equipment in semiconductor fabrication lines and contamination of entire fabrication lines is a concern that needs to be seriously addressed. Copper deposition by electroplating, electroless plating, or chemical vapor deposition (CVD) methods on wafers or substrates is known to leave copper residues on the backside of wafers. The backside copper residues may contaminate various wafer handlers and equipment in semiconductor fabrication lines. Copper decontamination of process equipment and/or the entire fabrication line typically is expensive.
The present invention addresses these and other problems by providing a process for removing material from a substrate. The material is exposed to an aqueous solution comprising about 4% to about 30% of at least one acid and at least one surfactant.
Also, the present invention provides a solution for removing metal from a substrate. The solution includes an aqueous solution of about 4% to about 30% of at least two acids. At least one surfactant is also included in the solution.
Furthermore, the present invention includes a system for removing metal from a substrate. The system includes a vessel for receiving the substrate and a solution for removing material from the substrate. The vessel includes at least one drain for draining the solution and at least one inlet for introducing the solution into the vessel. The system also includes an aqueous solution comprising about 4% about 30% of at least one acid and at least one surfactant. The system also includes a solution reservoir that includes at least one inlet and at least one drain. Connections permit solution to flow between the vessel and the solution reservoir. A pump pumps solution from the solution reservoir to the vessel. A cathode and an anode are arranged in the solution reservoir for removing from the solution material removed from the substrate. The system also includes a power source connected to the anode and the cathode.
Still other objects and advantages of the present invention will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described only the preferred embodiments of the invention, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.